Strain mediated bandgap reduction, light spectrum broadening, and carrier mobility enhancement of methylammonium lead/tin iodide perovskites

Density functional theory calculations are performed to study the electronic and optical properties of methylammonium lead/tin iodide perovskites under hydrostatic strain. It is found that the bandgap is significantly reduced to only 80/14 meV in lead/tin iodide perovskites under a moderate −6%/−4% strain. Such bandgap narrowing consequently induces the redshift of light absorption spectrum of the perovskite material by extending the onset light absorption edge by 200 meV. Additionally, applying external strain is also found to lighten the electron effective mass for CH3NH3PbI3/CH3NH3SnI3, thus enhancing the carrier mobility which benefits the collection of photogenerated charge carriers